Thursday, September 5, 2013

Another Model Joins the Cold Winter Prediction

Another weather model has joined the ranks of those predicting a colder than normal winter across a rather large portion of the country in coming months.

This is the Constructed Analog, or CA model from the Climate Prediction Center. It projects positive temperature anomalies to develop across the Bering Sea and Greenland areas, which may indicate positive height anomalies (high pressure) in those regions. For all intents and purposes, let's assume high pressure anomalies do exist in these two regions of positive temperature anomalies. This then leads to colder than normal temperatures flowing southeast from western Canada, spreading across the Plains, Midwest and even towards the Gulf Coast. This is actually not that far off from other forecasts made by other models, and this strengthens the argument for a colder than normal winter.

500 millibar height forecasts for the December-January-February period basically confirm the assumptions we made earlier in this post with the temperature anomalies. We see persistent positive height anomalies across the northern Pacific and Bering Sea. This is a very good sign for the chances of stratospheric warming events, which, if the atmospheric pattern is right, can allow for frigid air to move into North America. Multiple forecasts have been indicative of this positive height anomaly presence in the North Pacific, and the CA model's projection of this factor only aids in its credibility. We also see an elongated positive height anomaly swath across eastern Canada, Greenland and into northwest Europe. This is supportive of the negative North Atlantic Oscillation phenomenon, which permits a flow of cold air and enhanced coastal storm potential mainly in the Northeast, but the cold weather can spread across a wide portion of land east of the Mississippi.

So what does all of this mean? The long range models seem to be coming together, suggesting that a cold winter may really be on the way. I've been seeing more and more evidence that such a winter may be unfolding in just a few months, and this new model projection only increases my confidence.